1. Field of the Invention
The instant invention relates to novel liquid membrane formulations, i.e., emulsions, which comprise an aqueous interior phase and a water-immiscible exterior phase; said water-immiscible exterior phase comprising an ethylene vinyl acetate copolymer and a solvent for this polymer. These compositions may additionally contain a water insoluble surfactant to stabilize the emulsions. In the most preferred embodiment, the aqueous interior phase comprises a strong acid, for example, from about 1 to 10 percent by weight sulfuric acid. These emulsions are useful in liquid membrane processes for the separation of dissolved components from aqueous solution. Emulsions of the instant invention are characterized as showing very low swelling when contacted with aqueous solutions, especially at higher temperatures and thus are especially effective for use in the treatment of sour water feed streams by the liquid membrane technique.
2. Description of the Prior Art
In U.S. Ser. No. 382,466, filed July 25, 1973, now abandoned in the names of N. N. Li and R. P. Cahn, a process for removing the salt of a weak acid and a weak base from solution by means of the liquid membrane technology disclosed in U.S. Pat. Nos. 3,410,794, 3,617,546, and 3,779,907, all herein incorporated by reference, is disclosed. The process disclosed in U.S. Ser. No. 382,466 utilizes the liquid membrane technology to remove either the weak acid or weak base or their hydrolysis products from solution by permeating through the external phase of the liquid membrane emulsion and converting same into a nonpermeable form in the interior phase. Simultaneously the weak acid or weak base or the hydrolysis products thereof is stripped from solution by means of an inert gas. This process has been found to be most effective when run at high temperatures, for example 80.degree.C. It has been found, however, that, at temperatures in this range, many liquid membrane formulations, i.e., water-in-oil emulsions, are unsatisfactory, that is emulsion swelling, haziness of the treated water, etc., become problems. In the process of this invention, these problems are solved by means of novel formulations which may be used at temperatures of up to 95.degree.C.